1. Field of the Invention
The present disclosure herein relates to a semiconductor device, and more particularly, to a resistance variable memory device and a method of fabricating the resistance variable memory device.
2. Description of the Related Art
Generally, semiconductor memory devices may be classified into volatile memory devices and nonvolatile memory devices. Volatile memory devices lose stored data when power supply is interrupted. Examples of volatile memory devices include Dynamic Random Access Memories (DRAMs) and Static Random Access Memories (SRAMs). Meanwhile, nonvolatile memory devices do not lose stored data even when the power supply is interrupted. Examples of nonvolatile memory devices include Programmable ROMs (PROMs), Erasable PROMs (EPROMs), Electrically EPROMs (EEPROMs), and flash memory devices.
Recently, developments have been actively made on next-generation semiconductor memory devices such as a Ferroelectric Random Access Memory (FRAM), a Magnetic Random Access Memory (MRAM), and a Phase change Random Access Memory (PRAM) in accordance with the tendency toward high performance and low power of the semiconductor memory device. These next-generation semiconductor memory devices are made of materials that vary in resistance according to current or voltage and keep the resistance even though the current or voltage is interrupted.
Of these resistance variable memory devices, the phase change memory device (PRAM) utilizes phase change materials. Therefore, the phase change memory device (PRAM) is rapid in operation speed and has a structure that is advantageous for a high level of integration.
The phase change memory device stores information by using phase change materials. The phase change materials have two stable states (that is, crystalline state and amorphous state) having specific resistances different from each other. The specific resistance of the phase change material in the amorphous state is higher than that of the phase change material in the crystalline state. The phase change memory device can store data in phase change memory cells using the difference in specific resistance according to the state of the phase change material and can read the data stored in the phase change memory cells